Currently, the method commonly used for preparation of a color filter is a pigment dispersing method, which is simple and can impart good resistance to light, heat and chemicals, and can provide stable performances, etc. The pigment dispersing method is a method in which a pigment dispersed in a resin, with an alkali-soluble resin, a photo-polymerizable monomer, an initiator and other additives being added thereto, is coated onto a transparent glass substrate that has been provided with a black matrix, and then the coated glass substrate is subjected to exposure, development and other photoetching processes so as to form the respective color layers (i.e., red, green, and blue photoresists) of a color filter.
However, in the pigment dispersing process, the three components including pigment, dispersant and binder resin should form a stable combination such that the resultant pigment paste can maintain excellent stability. In the system, the binder resin functions to increase the viscosity, provide steric hindrance effect among the pigment particles and effectively prevent the occurrence of agglomeration. However, with decrease of the primary particle size of a pigment itself from less than 100 nm to the current level of less than 50 nm, the dispersion of the pigment becomes more and more difficult, as the surface energy of the pigment particles per se increases such that the pigment particles in the paste are very prone to agglomerate, which will influence the effect of coating the dispersion to configure a photoresist.
When a photosensitive resin composition comprising the aforesaid pigment dispersion is coated and subjected to exposure and development to form a resin film, the resin film has a high tendency to shrink during the post-baking process such that dents on the film surface and shrinkage of the side wall may be observed. Such shrinkage will impact the following processes, such as coating of other organic film(s), sputtering of ITO, or the like.